Here, a conventional juice dispenser is briefly explained as one of examples for a conventional beverage supply apparatus. The conventional juice dispenser comprises a syrup tank for containing thick juice, a cistern for containing water to dilute the thick juice, a thick juice nozzle for spouting the thick juice to a cup, a water nozzle for spouting the water to the cup, a thick juice tube of a plastic synthetic resin having the thick juice nozzle at one end thereof and connected to the syrup tank at an opposite end thereof, a water tube of a plastic synthetic resin having the water nozzle at one end thereof and connected to the cistern at an opposite end thereof, a coiled thick juice tube of stainless steel interposed at an appropriate position of the thick juice tube, a coiled water tube of stainless steel interposed at an appropriate position of the water tube, a cooling water tank for immersing the coiled thick juice and water tubes to cool the thick juice and the water flowing through the coiled thick juice and water tubes, and supply valves for controlling the thick juice and water nozzles to spout the thick juice and the water to the cup.
In operation, when the supply valves are opened, thick Juice and water supplied, respectively, from the syrup tank and the cistern are spouted from the nozzles to the cup. The spouted thick juice and water which have been cooled in passing through the coiled thick juice and water tubes are well mixed in the cup, so that a cup of juice which is adequately cooled it prepared.
In the conventional juice dispenser, the inner surfaces of the thick juice and water tubes including the coiled thick juice and water tubes are periodically (for instance, once a week) cleaned by inserting a cleaning member such as a string having a sponge like material on the outer surfaces thereof into the insides of the thick juice and water tubes which are emptied by draining the thick juice and the water from the thick juice and water tubes. This cleaning prevents funguses from breeding on the inner surfaces of the thick juice and water tubes.
In the conventional juice dispenser, however, there are disadvantages in that the thick juice is wasted to increase the cost of juice, because the thick juice is drained at each time of cleaning the thick juice and water tubes, and that the cleaning operation is troublesome, because it must be periodically carried out by draining the thick juice and the water and inserting the cleaning member into the thick juice and water tubes.
In order to eliminate the necessity of cleaning a beverage liquid-cooling tube the Japanese Patent Kokai No. 2-169992 has proposed a heat-exchanging apparatus for beverage supply in which the beverage liquid-cooling tube is made of fluorine resin or polyethylene to avoid the attachment of scale to the inner surface thereof.
The inventor has found in his experiment, however, that the use of a beverage liquid-cooling tube which is made of fluorine resin or polyethylene is insufficient to eliminate the cleaning thereof, because beverage liquid precipitates inorganic minerals such as Ca, Mg, etc. in accordance with the lowering of the solubility thereof, when it is cooled therein, and that such precipitated inorganic minerals are deposited on the inner surface of a beverage liquid tube on the side of the down-stream of the beverage liquid-cooling tube.